The present disclosure relates to a cylinder head.
Japanese Laid-Open Patent Publication No. 2008-57427 discloses a cylinder head adapted for arrangement on the upper side of a cylinder block. The cylinder head includes a cylinder head body and a camshaft housing. The cylinder head body is fixed to the upper surface of the cylinder block. The camshaft housing is fixed to the upper surface of the cylinder head body. Camshafts are accommodated in the camshaft housing and selectively open and close the intake valves and the exhaust valves.
The camshaft housing described in the aforementioned document includes two longitudinal frame bars extending in the axial direction of the camshafts. Multiple lateral frame bars extend between the longitudinal frame bars. The lateral frame bars are spaced apart at equal intervals in the axial direction of the camshafts. The lateral frame bars are arranged such that each adjacent two of the lateral frame bars are parallel to each other. A section recessed downward in a semi-circular shape is provided in the upper surface of each of the lateral frame bars as a bearing portion. Each of the bearing portions rotationally supports one of the camshafts. Bolt holes are provided at the opposite ends in the longitudinal direction of each lateral frame bar. The bolt holes extend through the lateral frame bars in the up-down direction. Bolts are inserted through the bolt holes and fix the camshaft housing to the cylinder head body.
Vibration is caused by driving an internal combustion engine or operating the vehicle and transmitted to the cylinder head. The frequency of the vibration transmitted to the cylinder head may coincide with the natural frequency of the longitudinal frame bars or the lateral frame bars, thus causing resonance in the longitudinal or lateral frame bars. Such resonance in the cylinder head may cause noise or damage and thus is undesirable.